Optical element and manufacturing method thereof

ABSTRACT

A flexible optical element useful for optical wiring is provided, in which a light emitting portion is disposed to a core end face of a flexible polymeric optical waveguide channel sheet having a film substrate clad, a core and a clad layer covering the core. A method which enables of manufacturing the optical element in a simple and convenient manner at a low cost is also provided.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to an optical element in which a lightemitting portion is disposed to a flexible polymeric optical waveguidechannel and a manufacturing method thereof.

[0003] 2. Description of the Related Art

[0004] Methods of manufacturing polymeric waveguide channels proposed sofar include, for example, (1) a method of impregnating a film with amonomer, selectively exposing a core portion to change the refractiveindex and bonding the film (selective polymerization method), (2) amethod of coating a core layer and a clad layer and then forming a cladportion by use of a reactive ion etching (RIE method), (3) a method ofusing photolithography of conducting exposure and development by use ofa UV-ray curable resin including a polymeric material with a lightsensitive material added therein (direct exposure method), (4) a methodof utilizing injection molding, and (5) a method of coating a core layerand a clad layer and then exposing the core portion to change therefractive index of the core portion (photo-bleaching method).

[0005] However, the selective polymerization method (1) involves aproblem in bonding the film, the method (2) or (3) increases the costbecause of the use of photolithography, and the method (4) has a problemin the accuracy of the diameter for the obtained core. Further, themethod (5) has a problem in that no sufficient difference for therefractive index can be obtained between the core layer and the cladlayer.

[0006] At present, only the methods (2) and (3) are practicallyexcellent in view of the performance but they involve the problem of thecost as described above. Then, none of the methods (1) to (5) issuitable to the formation of the polymeric waveguide channel to alarge-area, flexible plastic substrate.

[0007] Further, as a method of manufacturing a polymeric opticalwaveguide channel, a method of filling a polymer precursor material forcore into a pattern substrate (clad) in which a pattern of grooves ascapillaries is formed, then curing the same to prepare a core layer andbonding a planar substrate (clad) thereon has been known. However, sincethe polymer precursor material is thinly filled and cured not only inthe capillary grooves but also between the pattern substrate and theplanar substrate entirely to form a thin layer of a compositionidentical with the core layer, it involves a problem that light leaksthrough the thin layer.

[0008] As one method for overcoming the problems, David Hart hasproposed a method of manufacturing a polymeric optical waveguide channelby securing a patterned substrate in which a pattern of grooves ascapillaries is formed and a planar substrate by a clamping jig, thensealing a contact portion between the patterned substrate and the planarsubstrate with a resin, then decreasing the pressure and filling amonomer (diallylisophthalate) solution in the capillaries (JapanesePatent No. 3151364). This is a method of lowering the viscosity of thefilling material by use of a monomer instead of use of the polymerprecursor material as the core forming resin material, filling thematerial into the capillary by utilizing the capillary phenomenon whilekeeping the monomer from filling the portions other than the capillary.

[0009] However, since the method uses the monomer as the core formingmaterial, it involves a problem that the volumic shrinkage is large whenthe monomer is polymerized into a polymer to increase the transmissionloss of the polymeric optical waveguide channel.

[0010] Further, this is a complicated method of securing the patternedsubstrate and the planar substrate by clamping, or further seating thecontact portion with a resin, so that it is not suitable for massproduction and, as a result, the reduction of the cost cannot beexpected. Further, this method cannot be applied to the manufacture of apolymeric optical waveguide channel that uses a film in the thickness ofmm order or 1 mm or less as the clad.

[0011] Geroge M. Whitesides, et al. of Harvard University have recentlyproposed a method of a capillary tube micromold as one of lithographictechnics, as a new technology of preparing a nano-structure. This is amethod of preparing a master substrate by utilizing photolithography,transferring the nano-structure of the master substrate to apolydimethylsiloxane (PDMS) template by utilizing close adhesion andeasy releasability of PDMS and casting a liquid polymer into thetemplate by utilizing the capillary phenomenon and curing the same.Detailed illustrative descriptions are contained in SCIENTIFIC AMERICAN,September 2001 (Nikkei Science; December 2001).

[0012] Further, Kim Enoch, et al. in the group of George M. Whitesidesof Harvard University have filed, a patent application regarding acapillary tube micromold method (U.S. Pat. No. 6,344,198).

[0013] However, even when the manufacturing method described in thepatent is applied to the manufacture of the polymeric optical waveguidechannel, since the cross sectional area of the core portion in theoptical waveguide channel is small, it takes much time for forming thecore portion and is not suitable for mass production. Further, it has adrawback that the monomer solution causes a volumic change when it ispolymerized into a polymer, which changes the shape of the core toincrease the transmission loss.

[0014] Further, B. Michel, et al. of IBM Zurich Research Institute haveproposed a lithographic technology at high resolution using PDMS andreported that the technique can provide resolution at several tens nm.Detailed illustrative descriptions are contained in IBM J. REV. &DEV.vol. 45 No. 5, September 2001.

[0015] As described above, the soft lithographic technique or thecapillary tube micromold method using PMDS is a technique which hasrecently attracted attention mainly in the United States as thenano-technology.

[0016] However, in the manufacture of the optical waveguide channel byuse of the micromold method as described above, decrease of the volumicshrinkage during curing (accordingly, lowering of the transmission loss)and lowering of viscosity of the filled liquid (such as monomer) foreasier filling cannot be compatible with each other. Accordingly, whenpreferences is attached to the lowering of the transmission loss, theviscosity of the filled liquid cannot be lowered below a certain limit,which retards the filling speed and mass production cannot be expected.Furthermore, the micromold method is based on the premise of using glassor silicon substrates for the substrates and use of a flexible filmsubstrate is not taken into consideration.

[0017] By the way, in recent IC technology or LSI technology, attentionhas been focused on conducting optical wiring between apparatuses,between boards in an apparatus and within chips for improving theoperation speed or the integration degree instead of conducting electricwiring at high density.

[0018] As the device for optical wiring, Japanese Patent Laid Open No.2000-39530, for example, describes an optical element for a polymericoptical waveguide channel having a core and a clad surrounding the core,which has a light emitting element and a light receiving element in thedirection of laminating a core and a clad, and having an incident sidemirror for incidence of light from the light emitting element to thecore and an exit side mirror for emission of light from the core to thelight receiving element in which a clad layer is formed in a concaveshape at a portion corresponding to an optical channel from the lightreceiving element to the incident side mirror and from the exit sidemirror to the light receiving element to converge the light from thelight emitting element and the light from the exit side mirror. Further,Japanese Patent Laid-Open No. 2000-39531 describes an optical element inwhich light from the light emitting element enters the core end face ofa polymeric optical waveguide channel having a core and a cladsurrounding the core, wherein the light incident end face of the core isformed so as to provide a convex surface to the light emitting elementthereby converging the light from the light emitting element to suppressthe waveguide loss.

[0019] Further, Japanese Patent Laid-Open No. 2000-235127 describes aphotoelectronic integrated circuit in which a polymeric opticalwaveguide channel is assembled directly on a hybridized photoelectroniccircuit substrate in which electronic elements and light elements areintegrated.

[0020] By the way, when the element described above can be incorporated,for example, by being bent into the apparatus in the optical wiring, thedegree of freedom for designing the assembling of the optical wiring canbe increased and, as a result, integration degree of IC or LSI can beimproved.

[0021] However, since both of the optical element and thephotoelectronic integrated circuit lack in the flexibility, it isimpossible to incorporate the same, for example, by bending into theapparatus. Furthermore, since the optical element and thephotoelectronic integrated circuit have to be used with the core endface being formed into a convex shape or use of the mirror together,this inevitably complicates structure. The reason for requiringformation of the core end face into the convex shape or converging oflight by use of a lens as described above is that since thesemiconductor laser element as the light emitting element used, forexample, in the optical element generates a great amount of heat and theheat can no more be dissipated when the element is used merely in closeadhesion with the polymeric waveguide channel to cause operationfailure, it is necessary to provide a gap between the polymericwaveguide channel portion and the light emitting element to release heatwhile a diverging angle is present for the spot of a semiconductor laser(accordingly, light diverges as the gap is larger to bring about adifficulty in confining light in the optical waveguide channel).

[0022] Further, while both of the optical element and thephotoelectronic integrated circuit include the polymeric opticalwaveguide channel, both are manufactured by utilizing thephotolithographic method, which complicates the structure, causes aproblem such as liquid wastes and results in large environmental loads.

[0023] As described above, the flexible polymeric optical waveguidechannel sheet itself has not been provided at all so far and, inaddition, an idea of connecting the light emitting element to the endface of the polymeric optical waveguide channel sheet thereby forming anoptical element used for light optical wiring to avoid loss offlexibility has not been proposed at all.

SUMMARY OF THE INVENTION

[0024] This invention has been achieved in view of the foregoingproblems and intends to provide an optical element having flexibilitywhich is useful for optical wiring. This invention also intends toprovide a method of manufacturing an optical element of preparing theoptical element described above by a simple and convenient method at anextremely low cost According to an aspect of this invention, an opticalelement includes a flexible polymeric optical waveguide channel sheethaving a clad including a flexible film substrate, a core of a curingproduct of a UV-ray curable resin or a thermosetting resin disposed onthe clad and a clad layer formed so as to cover the core, and a lightemitting portion disposed to an end face of the optical waveguidechannel sheet.

[0025] According to another aspect of this invention, a method ofmanufacturing an optical element has the steps of: forming a layer of atemplate-forming resin material to an original substrate in whichconvexes for optical waveguide channel are formed, then peeling the sameto form a mold, and then cutting both ends of the mold to exposeconcaves corresponding to the convexes for optical waveguide channelformed to the mold, thereby preparing a template; closely adhering aflexible film substrate for clad having good adhesion with the templateto the template; bringing one end of the template which is adhered withthe flexible film substrate for clad into intimate contact with a UV-raycurable resin or a thermosetting resin to form a core and making theUV-ray curable resin or the thermosetting resin intrude by a capillaryphenomenon to the concaves of the template; curing the intruded UV-raycurable resin or the intruded thermosetting resin and peeling thetemplate from the flexible film substrate for clad; and forming a cladlayer on the flexible film substrate for clad formed with the core,thereby preparing a flexible polymeric optical waveguide channel sheetand then attaching a light receiving portion to the core end face of thesheet.

DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0026] Preferred embodiments of this invention will be described indetails based on the followings, wherein:

[0027]FIG. 1 is a conceptional view illustrating an example of anoptical element according to this invention;

[0028]FIG. 2 is a schematic view illustrating the steps of manufacturingan optical waveguide channel sheet of this invention; and

[0029]FIG. 3 is a schematic view illustrating other steps ofmanufacturing an optical waveguide channel sheet of this invention.

PREFERRED EMBODIMENT OF THE INVENTION

[0030] The optical element according to this invention includes aflexible polymeric optical waveguide channel sheet having a cladincluding a flexible film substrate, a core made of a curing product ofa UV-ray curable resin or a thermosetting resin disposed on the clad anda clad layer formed so as to cover the core, and a light emittingportion disposed to a core end face of the optical waveguide channelsheet. In the optical element according to the invention, since nooptical channel changing device such as a lens or a mirror is required,it is extremely simplified as the device. Further, in the opticalelement according to the invention, since the flexible polymeric opticalwaveguide channel sheet is used and the light emitting portion isdisposed to the end face thereof, flexibility is high over the entiredevice and the device can be deformed easily such as by bending or canbe incorporated in a deformed state into an integrated circuit togreatly enhance the integration degree of the integrated circuit inconjunction with the simplification of the element as described above.

[0031] The optical element according to this invention can be used forwide applications such as optical wiring in various stages, for example,optical wiring between apparatuses, between boards in an apparatus andbetween chips in the board.

[0032]FIG. 1 shows an example of an optical element according to thisinvention as a conceptional view. Shown in FIG. 1 are an optical element1, a lower clad (flexible film substrate clad) 2, a core 4, a clad layer6, a light emitting portion 7 and a light receiving portion 8respectively.

[0033] Further, the method of manufacturing the optical elementaccording to this invention is conducted by preparing a flexiblepolymeric optical waveguide channel sheet and then attaching a lightemitting portion to a core end face. The method of preparing theflexible polymeric optical waveguide channel sheet includes thefollowing steps of:

[0034] 1) forming a layer of a template-forming resin material to anoriginal substrate in which convexes for optical waveguide channels areformed, then peeling the same to form a mold and then cutting both endsof the mold so as to expose concaves corresponding to the convexes forthe optical waveguide channel formed in the mold to prepare a template,

[0035] 2) closely adhering a flexible film substrate for clad to form aclad having good adhesion with the template to the template,

[0036] 3) bringing one end of the template closely adhered with the filmsubstrate for clad into contact with a UV-curable resin or athermosetting resin to form a core and making the UV-ray curable resinor the thermosetting resin intrude by a capillary phenomenon into theconcaves of the template,

[0037] 4) curing the intruded UV-ray curable resin or the intrudedthermosetting resin and peeling the template from the flexible filmsubstrate for clad, and

[0038] 5) forming a clad layer on the flexible film substrate for cladto which the core is formed.

[0039] The method of manufacturing the flexible polymeric opticalwaveguide channel sheet according to this invention (hereinaftersometimes referred to simply as an optical waveguide channel sheet) isbased on the finding that when a flexible film substrate for clad havinggood adhesion with the template (hereinafter simply referred to as filmsubstrate for clad, film substrate, etc.) to the template as describedabove, the UV-ray curable resin or the thermosetting resin can be madeto intrude only into the concaves without causing a gap between thetemplate and the film substrate for clad except for the concavedstructure formed to the template even when both of them are not securedby use of a special unit (fixing unit as described in Japanese PatentNo. 3151364). The method of manufacturing the polymeric opticalwaveguide channel according to this invention is extremely simplified inview of the manufacturing steps, can manufacture the polymeric opticalwaveguide channel easily and enables manufacture of the polymericoptical waveguide channel at an extremely low cost compared with theexistent method of manufacturing the polymeric optical waveguidechannel. Further, the manufacturing method for the polymeric opticalwaveguide channel according to this invention can provide a flexiblepolymeric optical waveguide channel with less loss, at high accuracy andenabling easy attachment to various kinds of equipment. Further, themethod can freely set the shape and the like of the polymeric opticalwaveguide channel.

[0040] Then, in the method of manufacturing the optical elementaccording to this invention, since the light emitting portion may bemerely attached to the end face of the optical waveguide channel sheetmanufactured as described above, this is an extremely simple andconvenient method and capable of reducing the cost to such an extent ascomparison with optical elements using existent polymeric opticalwaveguide channels is unreasonable.

[0041] At first, the outline for the method of manufacturing the opticalwaveguide channel sheet according to this invention is to be explainedwith reference to FIG. 2.

[0042]FIG. 2A shows an original substrate to which convexes 12 foroptical waveguide channel are formed. At first, as shown in FIG. 2B, alayer 20 a of a template-forming resin material (for example, curedlayer of a curable resin) is formed to the surface of the originalsubstrate 10 to which convexes 12 for optical waveguide channel areformed. Then, the layer 20 a of the template-forming resin material isseparated from the original substrate 10 (mold transfer) and then bothends of the mold are cut so as to expose concaves 22 corresponding tothe convexes for optical waveguide channel formed to the mold to preparea template 20 (not illustrated) (refer to FIG. 2C).

[0043] A film substrate 30 for clad having good adhesion with thetemplate is adhered closely to the thus prepared template (refer to FIG.2D). Then, one end of the template is in contact with a curable resin 40a and the resin is made to intrude into the concaves 22 of the templateby utilizing the capillary phenomenon. FIG. 2E shows the state where thecurable resin is filled in the concaves of the template. Then, thecurable resin in the concaves is cured and then the template is peeled(not illustrated). As shown in FIG. 2F, convexes for optical waveguidechannels (cores) 40 are formed on the film substrate for clad.

[0044] Further, an optical waveguide channel sheet 60 according to thisinvention is manufactured by forming a core layer 50 to the core formingsurface of the film substrate for clad (refer to FIG. 2G).

[0045] Further, FIG. 3 shows an example of adhering a film as a clad onthe film substrate to which the core is formed. From FIG. 3A to FIG. 3Fare in common with the steps represented by FIG. 2A to FIG. 2F showingthe steps starting from the original substrate to the formation of thecore on the film substrate. FIG. 3G shows a step of bonding a film 52 toform a clad on the core forming the film substrate by use of an adhesive54.

[0046] The method of manufacturing the optical waveguide channel sheetaccording to the invention will be explained in the sequence of thesteps.

[0047] 1) Step of forming a layer of a template-forming resin materialto an original substrate in which convexes for optical waveguidechannels are formed, then peeling the same to form a mold and thencutting both ends of the mold so as to expose concaves corresponding tothe convexes for optical waveguide channels formed to the mold, therebypreparing a template

[0048] <Preparation of Original Substrate>

[0049] For the preparation of the original substrate in which convexesfor optical waveguide channels (convexes corresponding to the core) areformed, an existent method, for example, a photolithographic method canbe used with no particular restriction. Further, a method ofmanufacturing a polymeric optical waveguide channel by anelectrodeposition method or a photoelectrodeposition method filedpreviously by the present applicant (Japanese Patent Laid-Open No.2002-333538) is also applicable to the preparation of the originalsubstrate. The size of the convexes for optical waveguide channelsformed to the original substrate is properly determined depending, forexample, on the application of the polymeric optical waveguide channel.Generally, in a case of an optical waveguide channel for use in singlemode, a core of about 10 μm square is used, while a core of about 50 to100 m square is used in a case of an optical waveguide channel for usein multimode, but an optical waveguide channel having an even largercore portion such as about several hundreds μm may also be utilizeddepending on the application.

[0050] <Preparation of Mold>

[0051] The mold is prepared by forming a layer of the template resinmaterial to the optical waveguide channel surface of the originalsubstrate prepared as described above and peeling the same.

[0052] It is preferred that the template resin material can be peeledeasily from the original substrate and has mechanical strength anddimensional stability at or above a certain level as the template (usedrepetitively). The layer of the template resin material is formed of atemplate-forming resin which may be optionally incorporated with variousadditives.

[0053] Since individual optical waveguide channels formed to theoriginal substrate have to be transferred accurately to thetemplate-forming resin, the resin preferably has a viscosity at acertain limit or less, for example, about 2000 to 7000 mPa·s. Further,for controlling the viscosity, a solvent may be added to such an extentas the solvent gives no undesired effect.

[0054] For the template-forming resin, a curable silicone resin(thermosetting or room temperature curing type) is preferably used witha view point of peeling property, mechanical strength and dimensionalstability. Further, the resin of the type described above and a liquidresin of low molecular weight is preferably used since a sufficientpenetrating property is expected. The viscosity of the resin ispreferably about 500 to 7,000 mPa·s, and, further preferably, about 2000to 5000 mPa·s.

[0055] As the curable silicone resin, those containing methyl siloxanegroup, ethyl siloxane group or phenyl siloxane group are preferred and acurable dimethyl siloxane resin is particularly preferred.

[0056] Further, it is desirable that releasing treatment such as coatingof a releasing agent is applied in advance to the original substrate topromote releasing from the template.

[0057] The template resin material layer is formed to the opticalwaveguide channel surface of the original substrate, for example, byforming a layer of a template-forming resin by a method of coating orcasting the template-forming resin to the surface and then applyingdrying treatment or curing treatment as required.

[0058] The thickness for the template resin material layer is properlydetermined with the handleability as the template taken intoconsideration and, generally, it is appropriately about from 0.1 to 50mm.

[0059] Subsequently, the template resin material layer and the originalsubstrate are peeled to form a mold.

[0060] <Preparation of Template>

[0061] Then, both ends of the mold are cut so as to expose concavescorresponding to the convexes for optical waveguide channel formed tothe mold to prepare a template. The both ends of the mold are cut forexposing the concaves for making the UV-ray curable resin or thethermosetting resin intrude by the capillary phenomenon to the concavesof the template in the subsequent step.

[0062] It is preferred that the surface energy of the template is from10 dyne/cm to 30 dyne/cm, more preferably, within a range from 15 dyneto 24 dyne/cm from a viewpoint of close adhesion with the substratefilm.

[0063] Preferably, Share rubber hardness of the template is 15 to 80,preferably, 20 to 60 from a viewpoint of the mold forming performanceand the peeling property.

[0064] It is preferred that the surface roughness of the template(square mean roughness (RMS)) is 0.5 μm or less, preferably, 0.1 μm orless from a viewpoint of the mold formation performance.

[0065] 2) Step of Closely Bonding Film Substrate for Clad of Good CloseAdhesion with Template to Template

[0066] Since the optical element according to this invention is used foroptical wiring in various stages, the material for the flexible filmsubstrate is selected depending on the application of the opticalelement while considering, for example, optical characteristics such asrefractive index and light transmittance, mechanical strength, heatresistance, adhesion with the template and flexibility. The film caninclude, for example, cycloaliphatic acrylic film, cycloaliphatic olefinfilm, cellulose triacetate film and fluoro resin-containing films. It isdesirable that the refractive index of the film substrate is less than1.55 and, preferably, less than 1.53 in order to ensure the differenceof the refractive index with respect to that of the core.

[0067] As the cycloaliphatic acryl film, OZ-1000, OZ-1100 and the likein which alicyclic hydrocarbon such as tricyclodecane is introduced intothe ester substituents are used.

[0068] Further, the cycloaliphatic olefin film can include those havinga norbornene structure in the main chain and those having a norbornenestructure in the main chain and having polar groups such as alkyloxycarbonyl group (alkyl groups of 1 to 6 carbon atoms or cycloalkylgroups) on the side chain. Among them, the cycloaliphatic olefin resinshaving the norbornene structure in the main chain as described above andpolar groups such as alkyloxy carbonyl groups on the side chain areparticularly suitable for the manufacture of the optical waveguidechannel sheet of this invention since they have excellent opticalcharacteristics such as a low refractive index (refractive index ofabout 1.50, and capable of ensuring the difference of refractive indexto that of the core and clad) and high optical transmittance, and areexcellent in close adhesion with the template as well as in heatresistance.

[0069] Further, the thickness of the film substrate is selected withflexibility, rigidity and easy handlability taken into considerationand, generally, it is preferably about 0.1 mm to 0.5 mm.

[0070]3) Step of Bringing One End of Template Adhered with FilmSubstrate for Clad into Contact with UV-Ray Curable Resin orThermosetting Resin as Core and Making UV-Ray Curable Resin orThermosetting Resin Intrude by Capillary Phenomenon into Concaves ofMold

[0071] In this step, for filling the UV-ray curable resin and thethermosetting resin by the capillary phenomenon into a gap formedbetween the mold and the film substrate (concaves of the template), itis necessary that the UV-ray curable resin and the thermosetting resinused have a sufficient low viscosity to enable filling and that therefractive index of the curable resin after curing is higher than thatof the polymeric material constituting the clad (0.02 or more ofdifference to that of the clad). In addition, for reproducing at highaccuracy an original shape of the convexes for optical wave guidechannel formed to the original substrate, it is necessary that thevolumic change of the curable resin before and after curing is small.For example, decrease in the volume causes waveguide loss. Accordingly,it is desirable for the curable resin that the volumic change is aslittle as possible and it is desirably 10% or less, preferably, 6% orless. Lowering of the viscosity by the use of a solvent is preferablyavoided since this increases the volumic change before and after curing.

[0072] Accordingly, it is preferred that the viscosity of the curableresin is from 10 mPa·s to 2000 mPa·s, preferably, 20 mPa·s to 1000 mPa·sand, further preferably, 30 mPa·s to 500 mPa·s.

[0073] Further, epoxy type, polyimide type, UV-ray curable acryl typeresins are used preferably as the UV-curable resin.

[0074] Further, in this step, for promoting the filling of the UV-raycurable resin or the thermosetting resin by the capillary phenomenon tothe concaves of the mold by bringing one end of the template adheredwith the film substrate into contact with the curable resin or thethermosetting resin as a core, it is desirable that the entire system isdepressurized (to about 0.1 to 2000 Pa). Instead of depressurizing theentire system, it may be sucked by a pump from an end different from theone in contact with the curable resin, or it may be pressurized at oneend in contact with the curable resin.

[0075] Further, for promoting the filling, it is also an effectivemeasure to further lower the viscosity of the curable resin bypreviously heating the curable resin to be in contact with one end ofthe template instead of or in addition to the depressurization orpressurization described above.

[0076] It is necessary that the refractive index of the curing productof the UV-ray curable resin or the thermosetting resin of the core isgreater than that of the film substrate as the clad (including the cladlayer in the subsequent step (5)) and it is 1.53 or, more preferably,1.55 or more. The difference of the refractive index between the clad(including the clad layer in the subsequent step (5)) and the core is0.02 or more and, preferably, 0.05 or more.

[0077] 4) Step of Curing Intruded UV-Ray Curable Resin or ThermosettingResin and Peeling Template From Film Substrate

[0078] The intruded UV-ray curable resin or the thermosetting resin iscured. For curing the UV-ray curable resin, UV-ray lamp, UV-ray LED orUV ray irradiation apparatus and the like are used. Further, for curingthe thermosetting resin, heating in an oven is adopted.

[0079] Further, the template used in the steps (1) to (3) above can alsobe used as it is as the clad layer, in which it is not necessary to peelthe template and it can be used as it is as the clad layer.

[0080] 5) Step of Forming Clad Layer on Film Substrate Formed with Core

[0081] A clad layer is formed on a film substrate formed with a core.The clad layer includes, for example, films (for example, a filmsubstrate as used in the preceding step (2) is used in the same manner),layers formed by coating and curing curable resins (UV-ray curableresins, thermosetting resins) and polymeric films obtained by coatingand drying a solvent solution of a polymeric material. When the film isused as the clad layer, the film is bonded by use of an adhesive inwhich the refractive index of the adhesive is preferably near to therefractive index of the film.

[0082] The refractive index of the clad layer is, preferably, 1.55 orless and, more preferably, 1.53 or less for ensuring the difference ofthe refractive index relative to that of the core. Further, it ispreferred that the refractive index of the clad layer is equal with therefractive index of the film of the substrate from a viewpoint ofconfinement of light.

[0083] In the manufacturing method of the optical waveguide channelsheet according to this invention, combined use of a thermosettingsilicone resin, in particular, a thermosetting dimethyl siloxane resinas the template material and a cycloaliphatic olefin resin having anorbornene structure in the main chain and having polar groups such asalkyl oxycarbonyl groups on the side chain as the film material providesparticularly high adhesion between both of them and can fill theconcaves with the curable resin rapidly by the capillary phenomenon evenwhen the cross sectional area of the concaves is extremely small (forexample, 10×10 μm rectangular shape).

[0084] Further, the template can also be used as the clad layer, inwhich it is preferred that the refractive index of the template is 1.5or less and the template is, applied with ozone treatment for improvingthe adhesion between the template and the core material Then a lightemitting portion is attached to the core end face of the opticalwaveguide channel sheet prepared as described above. For improving theintegration degree of an integrated circuit, a surface light emittinglaser array (VCSEL) is used preferably for the light emitting portion.

[0085] Since a semiconductor laser device of the surface light emittinglaser array generates a great amount of heat, it is necessary to keep adistance between the semiconductor laser device and the core end face inorder to prevent undesired effects by the heat generation. However,since the semiconductor laser beam has a diverging angle, when thedistance exceeds a certain limit, the laser beam spot diameter at thecore end face exceeds an allowable value for the core (for example, theallowable diameter is 45 μm for a core diameter of 50 μm).

[0086] However, with the spot diameter of the semiconductor laser andthe diverging angle of the laser beam in the surface light emittinglaser taken into consideration, the semiconductor layer and the core endface can be spaced apart to such an extent as sufficiently avoiding theeffect of heat generation without using the lens or the like.

[0087] For example, in a case of attaching a surface light emittinglaser array with a spot diameter of the semiconductor laser of 10 μm,the beam diverging angle of 25° and an array distance of 250 μm(VCSEL-AM-0104, manufactured by Fuji Xerox Co., Ltd.) to the end face ofa multimode polymeric optical waveguide channel sheet with the corediameter of 50 μm, since the laser beam spot diameter at the coresurface is allowable to about 45 μm, the semiconductor layer and thecore end face can be spaced apart up to 79 μm as the maximum. When thelaser beam diameter at the core end face is set to 30 μm, the distancebetween the semiconductor laser and the core end face is about 45 μm.With such an extent of the distance, generated heat can be releasedsufficiently even when considering the temperature elevation of thesemiconductor laser device up to about 100° C.

[0088] Accordingly, a laser array in which the spot diameter of thesemiconductor laser is 1 to 20 μm and the diverging angle of the laserbeam is about 5° to 30° in the surface light emitting laser array isused preferably. The array distance is preferably about 100 to 500 μm.For example, VCSEL-AM-0104, VCSEL-AM-0112 and the like manufactured byFuji Xerox Co., Ltd. are used preferably.

[0089] Further as a unit that keeps the distance between the core endface of the optical waveguide channel sheet and the semiconductor laserof the surface light emitting laser array as described above, a frame ofa sufficient height to keep the distance may be disposed to the surfaceof the light emitting laser array, and the frame and the opticalwaveguide channel sheet are fixed, for example, by use of adhesives.

[0090] Further, in the optical element according to this invention, alight receiving portion may be disposed in addition to the lightemitting portion. A photodiode array or the like is used preferably asthe light emitting portion. For the photodiode array, those having asensitivity in the same ultraviolet wavelength as the surface lightemitting laser array and having high sensitivity such as Si photodiodearray or GaAs photodiode array are preferred.

EXAMPLES

[0091] This invention is to be explained more specifically withreference to examples but the invention is not restricted to suchexamples.

Example 1

[0092] After coating a thick film resist (SU-8, manufactured byMicrochemical Co.) to an Si substrate by a spin coating method, it wasprebaked at 80° C., exposed through a photomask and developed to formfour convexes each of a square cross section (width: 50 μm, height: 50μm) as shown in FIG. 1. The distance between each of the convexes wasset to 250 μm. Then, it was postbaked at 120° C. to prepare an originalsubstrate for manufacturing an optical waveguide channel core.

[0093] Then, after coating a releasing agent to the original substrate,a thermosetting dimethyl siloxane resin (SYLGARD 184, manufactured byDow Corning Asia Co.) was cast and cured by heating at 120° C. for 30minutes and then peeled to prepare a mold having concaves correspondingto the convexes of the square cross section (mold thickness: 3 mm).Further, both ends of the mold were cut to prepare an input/outputportion for the following UV-ray curable resin to form a template.

[0094] The template and a film substrate of 188 μm thickness (ARTONfilm, manufactured by Nippon Synthesis Rubber Co., refractive index:1.510) slightly larger than the template were adhered closely. Then,when a UV-ray curable resin at a viscosity of 1300 mPa·s (PJ3001,manufactured by JSR Co.) was dripped by several drops to theinput/output portion at one end of the template, the concaves werefilled with the UV-ray curable resin by the capillary phenomenon. Then,the upper portion of the template was irradiated with UV-light at 50mW/cm² for 5 minutes to conduct UV curing. When the template was peeledfrom the ARTON film, a core of the same shape as that of the convexes ofthe original substrate was formed on the ARTON film. The refractiveindex of the core was 1.591.

[0095] Then, after coating a UV-ray curable resin having a refractiveindex after curing of 1.510 which is identical with that of the ARTONfilm (manufactured by JSR Co.) over the entire core forming surface ofthe ARTON film, w-light at 50 mW/cm² was applied for 5 minutes toconduct UV-ray curing (film thickness after curing was 10 μm). Aflexible optical waveguide channel sheet (50 mm×300 mm) was obtained.The loss of the polymeric optical waveguide channel was 0.33 dB/cm.

[0096] Then, a 1×4 surface light emitting laser array (VCSEL-AM-0104,manufactured by Fuji Xerox Co., Ltd., with a spot diameter of thesemiconductor laser of 10 μm, a beam diverging angle of 25° and an arraydistance of 250 μm) was attached to the core end face of the opticalwaveguide channel sheet prepared as described above at a gap of 50 μm toform a flexible polymeric waveguide channel with the surface lightemitting laser array.

Example 2

[0097] An original substrate for preparing an optical waveguide channelhaving four convexes each of a square cross section (width: 50 μm,height: 50 μm) was by the same method as in Example 1. Then, afterpreparing a mold in the same manner as in Example 1, both ends were cutto form a template. The template and an ARTON film (thickness: 180 μm)slightly larger than the template were closely adhered and, when severaldrops of a thermosetting resin at a viscosity of 500 mPa·s (manufacturedby JSR Co.) were dripped to the input/output portion at one end of thetemplate, the concaves were fill with the thermosetting resin by thecapillary phenomenon. It was thermally cured by heating for 30 minutesin an oven at 130° C. When the template was peeled from the ARTON film,a core of the same shape as the original substrate convexes was formedon the ARTON film. The refractive index of the core was 1.570. Further,after coating, a thermosetting resin with the refractive index aftercuring being identical with the ARTON film (manufactured by JSR Co.)over the entire surface of the core forming surface of the ARTON film,it was heat (film thickness after curing: 10 μm). A flexible opticalwaveguide channel sheet (50 mm×300 mm) was obtained. The loss of thepolymeric optical waveguide channel was 0.33 dB/cm.

[0098] Then, a 1×4 surface light emitting laser array (VCSEL-AM-0104,manufactured by Fuji Xerox Co., Ltd.) was attached at a 50-μm gap to thecore end face of the optical waveguide channel sheet prepared asdescribed above to form a polymeric waveguide channel with the surfacelight emitting laser array.

Example 3

[0099] An original substrate for preparing an optical waveguide channelhaving for convexes each of a square cross section (width: 50 μm,height: 50 μm) by the same method as in Example 1. Then, after preparinga mold in the same manner as in Example 1, both ends were cut to form atemplate. The template and an ARTON film (thickness: 180 μm) slightlylarger than the template were closely adhered and several drops of athermosetting resin at a viscosity of 1300 mPa·s (PJ3001, manufacturedby JSR Co.) were dripped to the input/output portion at one end of thetemplate. The template and ARTON film were adhered closely, which wereplaced in a container depressurized by a vacuum pump (1.0 Pa). TheUV-ray curable resin was filled into the concaves instantly by thecapillary phenomenon. After taking out the same from the container, theupper portion of the template was irradiated with UV-light at 50 mW/cm²for 5 minutes to conduct curing and the template was peeled. A core witha refractive index of 1.591 was formed on the ARTON film.

[0100] Further, after coating a thermosetting resin with the refractiveindex after curing of 1.510 which is identical with that of the ARTONfilm (manufactured by JSR Co.) over the entire surface of the coreforming surface of the ARTON film, it was cured by applying UV-rays of50 mW/cm² for 10 minutes (film thickness after curing: 10 μm). Aflexible optical waveguide channel sheet (50 mm×300 mm) was obtained.The loss of the polymeric optical waveguide channel was 0.33 dB/cm.

[0101] Then, a 1×4 surface light emitting laser array (VCSELAM-0104,manufactured by Fuji Xerox Co., Ltd.) was attached at a 50-μm gap to thecore end face of the optical waveguide channel sheet prepared asdescribed above to form a flexible polymeric waveguide channel with thesurface light emitting laser array.

Example 4

[0102] A flexible optical waveguide channel sheet (50 mm×300 mm) wasprepared in the same manner as in Example 3, except for closely adheringa template to an ARTON film, sucking from one end of the input/outputportion of the template by a diaphragm type suction pump (maximumsuction pressure: 33.25 KPa) instead of dripping several drops of theUV-ray curable resin to the input/output portion at the other end of thetemplate and placing the same in a container depressurized by the vacuumpump in Example 3. The loss of the polymeric optical waveguide channelwas 0.33 dB/cm.

[0103] Then, a 1×4 surface light emitting laser array (VCSEL-AM-0104,manufactured by Fuji Xerox Co., Ltd.) was attached at a 50-μm gap to thecore end face of the optical waveguide channel sheet prepared asdescribed above to form a flexible polymeric waveguide channel with thesurface light emitting laser array.

Example 5

[0104] The steps up to formation of the core on the ARTON film inExample 1 were conducted by the same procedures.

[0105] Then, the ARTON film (thickness: 188 μm) was bonded to the coreforming surface of the ARTON film by use of an adhesive at a refractiveindex of 1.510 (manufactured by JSR Co.) to prepare a flexible opticalwaveguide channel sheet The loss of the polymeric waveguide channel was0.33 dB/cm.

[0106] Then, a 1×4 surface light emitting laser array (VCSEL-AM0104,manufactured by Fuji Xerox Co., Ltd.) was attached at a 50--μm gap tothe core end face of the optical waveguide channel sheet (50 mm×30 mm)prepared as described above to form a flexible polymeric waveguidechannel with the surface light emitting laser array.

Example 6

[0107] A template was prepared by the same method as in Example 1. Then,the template and an ARTON film (thickness: 188 μm) slightly larger thanthe template were adhered closely. Several drops of a UV-ray curableresin at a viscosity of 100 mPa·s (manufactured by NTT-AT Co.) weredripped by to the input/output portion at one end of the template. Whensuction was conducted by a vacuum pump from the other end of theinput/output portion of the template, the concaves were filled with aUV-ray curable resin by the capillary phenomenon. Then, the upperportion of the template was irradiated with UV-light at 50 mW/cm² for 5minutes to conduct UV-ray curing. When the template was peeled from theARTON film, a core of the same shape as the original base convexes wasformed on the ARTON film. The refractive index of the core was 1570.

[0108] Then, an ARTON film (188 μm thickness) was bonded to the coreforming surface of the ARTON film by use of an adhesive at a refractiveindex of 1.510 (manufactured by JSR Co.) to prepare a flexible opticalwaveguide channel sheet (50 mm×300 mm). The loss of the polymericoptical waveguide channel was 0.15 dB/cm.

[0109] Then, a 1×4 surface light emitting laser array (VCSEL-AM-0104,manufactured by Fuji Xerox Co., Ltd.) was attached at a 5 μm gap to thecore end face of the optical waveguide channel sheet prepared asdescribed above to form a flexible polymeric waveguide channel with thesurface light emitting laser array.

Example 7

[0110] An optical waveguide channel sheet (50 mm×300 mm) was prepared inthe same manner as in Example 1 except for heating the UV-ray curableresin in advance to 70° C., dripping several drops of the resin to theinput/output portion at one end of the template and then irradiating thesame with UV-rays after lowering the temperature to the room temperaturein Example 1. The loss of the polymeric optical waveguide channel was0.35 dB/cm.

[0111] Then, a 1×4 surface light emitting laser array (VCSEL-AM-0104,manufactured by Fuji Xerox Co., Ltd.) was attached at a 50-μm gap to thecore end face of the optical waveguide channel sheet prepared asdescribed above to form a polymeric waveguide channel with the surfacelight emitting laser array.

[0112] Since the optical channel changing device such as a lens or amirror is not necessary, the optical element according to this inventioncan be simplified extremely as a device. Further, since the flexiblepolymeric optical waveguide channel sheet is used and the light emittingportion is disposed to the end face thereof, the entire device has highflexibility and can be deformed simply by bending and the like. Further,it can be incorporated in a deformed state into an integrated circuitand can improve the integration degree of the integrated circuit greatlyin conjunction with the simplification of the device.

[0113] The optical element according to this invention can be used forwide applications such as optical wiring in various states, for example,optical wiring between apparatuses, between boards in an apparatus andbetween chips in a board Further, in the manufacturing method of theoptical element according to this invention, since it can be conductedby merely preparing a flexible polymeric optical waveguide channel sheetby an extremely simplified and low-cost method and then attaching thelight emitting portion to the end face of the flexible polymeric opticalwaveguide channel sheet, this is an extremely simple and convenientmethod and can attain cost reduction to such an extent as comparisonwith optical elements using the existent polymeric optical waveguidechannels is unreasonable.

[0114] The entire disclosure of Japanese Patent Application No.2002-187474 filed on Jun. 27, 2002 including specification, claims,drawings and abstract is incorporated herein by reference in itsentirety.

What is claimed is:
 1. An optical element comprising a flexiblepolymeric optical waveguide channel sheet having a clad including aflexible film substrate, a core of a curing product of a UV-ray curableresin or a thermosetting resin disposed on the clad and a clad layerformed so as to cover the core, and a light emitting portion disposed toan end face of the optical waveguide channel sheet.
 2. An opticalelement according to claim 1, wherein the light emitting portion is asurface light emitting laser array having a plurality of emittingelements.
 3. An optical element according to claim 2, wherein a distancebetween the respective emitting elements in the surface light emittinglaser array is from 20 μm to 2 mm.
 4. An optical element according toclaim 1, further comprising a light receiving portion disposed toanother end face in the flexible polymeric optical waveguide channelsheet.
 5. An optical element according to claim 4, wherein the lightreceiving portion has a photodiode array.
 6. A method of manufacturingan optical element comprising the steps of: forming a layer of atemplate-forming resin material to an original substrate in whichconvexes for optical waveguide channel are formed, then peeling the sameto form a mold, and then cutting both ends of the mold to exposeconcaves corresponding to the convexes for optical waveguide channelformed to the mold, thereby preparing a template; closely adhering aflexible film substrate for clad having good adhesion with the templateto the template; bringing one end of the template which is adhered withthe flexible film substrate for clad into intimate contact with a UV-raycurable resin or a thermosetting resin to form a core and making theUV-ray curable resin or the thermosetting resin intrude by a capillaryphenomenon into the concaves of the template; curing the intruded UV-raycurable resin or the intruded thermosetting resin and peeling thetemplate from the flexible film substrate for clad; and forming a cladlayer on the flexible film substrate for clad formed with the core,thereby preparing a flexible polymeric optical waveguide channel sheetand then attaching a light receiving portion to the end face of thesheet.
 7. A method of manufacturing an optical element according toclaim 6, wherein the clad layer is formed by coating and then curing theUV-ray curable resin or the thermosetting resin.
 8. A method ofmanufacturing an optical element according to claim 6, wherein the cladlayer is formed by bonding a film for clad by use of an adhesive havinga refractive index which is nearly equal with that of the film.
 9. Amethod of manufacturing an optical element according to claim 6, whereinthe layer of the template-forming resin material is a layer formed bycuring a curable silicone resin.
 10. A method of manufacturing anoptical element according to claim 6, wherein surface energy of thetemplate is from 10 dyne/cm to 30 dyne/cm.
 11. A method of manufacturingan optical element according to claim 6, wherein Share rubber hardnessof the template is from 15 to
 80. 12. A method of manufacturing anoptical element according to claim 6, wherein surface roughness of thetemplate is 0.5 μm or less.
 13. A method of manufacturing an opticalelement according to claim 6, wherein light transmittance of thetemplate is 80% or more in a region from 350 nm to 700 nm.
 14. A methodof manufacturing an optical element according to claim 6, wherein athickness of the template is from 0.1 mm to 50 mm.
 15. A method ofmanufacturing an optical element according to claim 6, wherein arefractive index of the flexible film substrate for clad is 1.55 orless.
 16. A method of manufacturing an optical element according toclaim 6, wherein the flexible substrate for clad comprises acycloaliphatic olefin resin film.
 17. A method of manufacturing anoptical element according to claim 16, wherein the cycloaliphatic olefinresin film is a resin film having a norbornene structure in a main chainand having polar groups in side chains.
 18. A method of manufacturing anoptical element according to claim 6, wherein a pressure in a system isreduced in the step of making the UV-ray curable resin or thethermosetting resin intrude by the capillary phenomenon into theconcaves of the template.
 19. A method of manufacturing an opticalelement according to claim 6, wherein a viscosity of the UV-ray curableresin or the thermosetting resin is from 10 mPa·s to 2000 mPa·s.
 20. Amethod of manufacturing an optical element according to claim 6, whereina diameter of the core is within a range from 10 μm to 500 μm.